Revealing the Band Structure of FAPI Quantum Dot Film and Its Interfaces with Electron and Hole Transport Layer Using Time Resolved Photoemission

Amelot, Dylan; Rastogi, Prachi; Martinez, Bertille; Gréboval, Charlie; Livache, Clément; Bresciani, Francesco Andrea; Qu, Junling; Chu, Audrey; Goyal, Mayank; Chee, Sang‐Soo; Casaretto, Nicolas; Xu, Xiang; Méthivier, Christophe; Cruguel, Hervé; Ouerghi, Abdelkarim; Nag, Angshuman; Witkowski, Nadine; Lhuillier, Emmanuel

doi:10.1021/acs.jpcc.9b10946

Cited by 13 publications

(20 citation statements)

References 41 publications

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“…d. Scheme of the band bending occuring in a p-type semiconductor film after turning-off the illumination. The figure is adapted with permission from ref 32 . Copyright (2020) American Chemical Society.…”

Section: Resultsmentioning

confidence: 99%

Time-Resolved Photoemission to Unveil Electronic Coupling between Absorbing and Transport Layers in a Quantum Dot-Based Solar Cell

Gréboval

Rastogi

et al. 2020

J. Phys. Chem. C

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Lead sulfide (PbS) colloidal quantum dots-based photodiodes are remarkable structures obtained via colloidal engineering because of their outstanding optoelectronic performances. They combine surface ligand engineering to design a p-n junction with all solution processability. Here we investigate the PbS diode electronic structure combining static and dynamic photoemissions with transport measurements. We show that the n-type nature of the Icapped PbS CQDs shifts the valence band away from the Fermi level compared to the thiol capped nanocrystals. This change in majority carriers can be probed using time resolved X-ray photoemission spectroscopy (TRXPS). We also prove that the photo-induced binding energy shift depends on the nanoparticle surface chemistry. Finally, we demonstrate the ability of TRXPS to selectively probe the electronic structure of each side of an interface. We explore the PbS/MoO3 interface used as hole extractor in the PbS solar cell, using this method. We demonstrate that the PbS layer photosensitizes the MoO3 layer and that the two layers have a quasi-rigid electrostatic coupling. We identify the band bending occurring on the PbS(EDT)/MoO3 to be a limiting factor for the device performance and suggest strategies to overcome this limitation.

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Section: Resultsmentioning

confidence: 99%

Time-Resolved Photoemission to Unveil Electronic Coupling between Absorbing and Transport Layers in a Quantum Dot-Based Solar Cell

Gréboval

Rastogi

et al. 2020

J. Phys. Chem. C

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“…In these fresh samples, the Pb 4f 7/2 component lies at 138.5 eV (the Pb 4f spin–orbit splitting results 4.9 eV) and the I 3d 5/2 component lies at 619.3 eV (the I 3d spin–orbit splitting results 11.5 eV), which can be attributed to the major presence of Pb–I bonds in these perovskites. 68 , 69 …”

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confidence: 99%

“…Moreover, we observed no significant peak attributable to Pb 0 (expected at 136.9 eV) and higher binding energy broadening that may point out to the formation of lead carbonate (PbCO 3 , at a binding energy of 139.3 eV). 68 , 69 In the case of aged FAPI (N 2 ) films, however, no traces from additional Pb 4f components have been observed, Figure 4 c. In addition to this, aging effects seem not to reduce the presence of I in these films, Figure 4 d. Instead, the Pb 4f and I 3d core levels attributed to the Pb–I bond appear to downshift by 0.3 eV in 7 days of aging, Figure 4 e. The behavior of the core level peaks of the FAPI (N 2 ) films observed over aging can be associated with a phase conversion from α-FAPI to δ-FAPI without any presence of intermediate products (such as PbO, PbCO 3 , etc.). 68 This transition implies a change in the Pb and I bonding nature as neighbor octahedra in δ-FAPI are no longer sharing iodine corners as in α-FAPI.…”

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confidence: 99%

Boosting Long-Term Stability of Pure Formamidinium Perovskite Solar Cells by Ambient Air Additive Assisted Fabrication

et al. 2021

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Due to the high industrial interest for perovskite-based photovoltaic devices, there is an urgent need to fabricate them under ambient atmosphere, not limited to low relative humidity (RH) conditions. The formamidinium lead iodide (FAPI) perovskite α-black phase is not stable at room temperature and is challenging to stabilize in an ambient environment. In this work, we show that pure FAPI perovskite solar cells (PSCs) have a dramatic increase of device long-term stability when prepared under ambient air compared to FAPI PSCs made under nitrogen, both fabricated with N -methylpyrrolidone (NMP). The T 80 parameter, the time in which the efficiency drops to 80% of the initial value, increases from 21 (in N 2 ) to 112 days (in ambient) to 145 days if PbS quantum dots (QDs) are introduced as additives in air-prepared FAPI PSCs. Furthermore, by adding methylammonium chloride (MACl) the power conversion efficiency (PCE) reaches 19.4% and devices maintain 100% of the original performance for at least 53 days. The presence of Pb–O bonds only in the FAPI films prepared in ambient conditions blocks the propagation of α- to δ-FAPI phase conversion. Thus, these results open the way to a new strategy for the stabilization in ambient air toward perovskite solar cells commercialization.

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“…A second key advantage of the hybrid material is the faster time response. Pristine PbS is well known to have a slow time response due to the presence of traps, 26 whereas perovskite is able to show fast time response. 23 Here, the time response is typically around 5 µs, Figure S 18.…”

Section: F Photoemission Signal Relative To the Valence Band For Fapi Pbs And Fapi/pbs (35% Pbs Content) Inset Is A Band Diagram For Fapimentioning

confidence: 99%

Pushing Absorption of Perovskite Nanocrystals into the Infrared

et al. 2020

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To date defect-tolerance electronic structure of Lead halide perovskite nanocrystals is limited to optical feature in the visible range. Here, we demonstrate that IR sensitization of formamidinium lead iodine (FAPI) nanocrystals array can be obtained by its doping with PbS nanocrystals. In this hybrid array, absorption comes from the PbS nanocrystals while transport is driven by the perovskite which reduces the dark current compared to pristine PbS. In addition, we fabricate a field-effect transistor using a high capacitance ionic glass made of hybrid FAPI/PbS nanocrystal arrays. We show that the hybrid material has an n-type nature with an electron mobility of 2 x 10 -3 cm 2 V -1 s -1 . However, the dark current reduction is mostly balanced by a loss of absorption. To overcome this limitation, we couple the FAPI/PbS hybrid to a guided mode resonator, that can enhance the infrared light absorption.

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Revealing the Band Structure of FAPI Quantum Dot Film and Its Interfaces with Electron and Hole Transport Layer Using Time Resolved Photoemission

Cited by 13 publications

References 41 publications

Time-Resolved Photoemission to Unveil Electronic Coupling between Absorbing and Transport Layers in a Quantum Dot-Based Solar Cell

Time-Resolved Photoemission to Unveil Electronic Coupling between Absorbing and Transport Layers in a Quantum Dot-Based Solar Cell

Boosting Long-Term Stability of Pure Formamidinium Perovskite Solar Cells by Ambient Air Additive Assisted Fabrication

Pushing Absorption of Perovskite Nanocrystals into the Infrared

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